Antibiotic Testing

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INTRODUCTION:
Over prescription and extensive use of antibiotics has caused antibiotic resistance at an shocking rate (Mezger et al.2014). The main aims of Antibiotic sensitivity testing is detecting possible drug resistance in common pathogens by in-vitro testing of bacterial cultures with antibiotics to determine susceptibility of bacteria to antibiotic therapy. The tests are frequently used when the etiologic agents are members of species capable of resistance to commonly prescribed drugs (Jenkins and Schuetz,2012). The most-widely used tests in clinical laboratories include Manual: Broth Microdilution, Disc Diffusion and E-test. Automated instruments: MicroScan walkaway, Vitek2 system and PhoenixBD tests are commercially used.
Manual:
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There are two types: Macrodilution in each test tube there is broth solution equal to or excess 1mL and Microdilution,test tubes contain smaller volumes of antimicrobial concentrations (Jenkins and Schuetz,2012). Both micro- and macro- dilution methods, present the lowest concentration where it is completely inhibited and is recorded as the minimal inhibitory concentration (MIC). MIC is the minimum concentration of an antibiotic that will inhibit the visible growth of a microorganism (McKenzie,2009).
The procedure for macrodilution involves preparing two-fold dilutions of antibiotics in a growth medium and dispensed into the test tubes. A standardized bacterial suspension of 1–5×105CFU/mL is introduced into tubes. The tubes are incubated overnight at 35°C, they are then observed for visible bacterial growth in form of turbidity (Jorgensen and Ferraro,2009). The core advantage of this process is it produces quantitative data allowing data to be precise and clear-cut. Allowing data to be generalisable, however research has critiqued the macrodilution method as being mundane, as it involves manual preparation of antibiotic solutions, increasing processing time. Furthermore increasing the possibility for errors occurring during preparation thus, negatively affecting final results. Each test requires a large amount of reagents and space, therefore problematic
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Automated systems are upcoming and in future will progress to a high degree of accuracy, the standardisation of the tests allows same results to be reproduced in different laboratories. The key advantage of automated systems is the high-speed result production. There is now a need to progress from manual tests, as they are long and labour-intensive, slowing result production. The principal disadvantage is the amount of time the manual tests take, with longer incubation periods and time spent preparing the equipment required. Therefore automated tests are more favourable and the increasing research will provide even better systems in the

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